They're called "rumble strips" -- rough lines in pavement designed to alarm drivers if they drift out of their lane -- and when Carver County installed 10 miles of them along the edge of Hwy. 10 last summer, they certainly did their job. They created a sudden and urgent noise anytime a car ventured onto the edge of the road.

Trouble was, they also annoyed residents, who complained loudly to the county.

"We thought it would save lives," Carver County Administrator Dave Hemze said. But the rumble strips were way too loud, the residents said. And when county officials checked for themselves, they had to agree.

"The noise was unbelievable," Hemze said. "You could hear it for about two miles."

Part of the problem, Hemze said, was that the county tried something relatively new. Instead of placing the white fog line marking the outside edge of the driving lane a few inches inside the rumble strips, the county placed the white line right on top of the rumble strips, in effect creating rumble stripes.

As a result, a lot more motorists were hitting the strips. And just months after the $12 million highway renovation project was completed last summer between Chaska and Waconia, the county paid another $40,000 to fill in the strips.

Wright's solution

About the same time, Wright County officials faced a similar situation. The county also had created rumble strips along Hwy. 35 east of Buffalo, which prompted residents to complain about the noise they created.

Wright County's solution: Instead of filling in the rumble strips, it would move the edge of the fog line in about 8 inches along 2,900 feet of curved roadway, so drivers aren't as likely to drift out as far as the rumble strips, according to Wayne Fingalson, the county engineer. The cost: $500.

"We put them in for a reason. They do work," Fingalson said. "Our County Board felt very strongly that they needed to stay."

The strips, also known as "audio tactile profiled markings," have been around for decades, first appearing on New Jersey highways in the early 1950s. Traffic engineers say they are effective in reducing accidents in a number of locations, including a 70 to 80 percent reduction in accidents caused by driving off the road.

Among the places using them with effectiveness is New Zealand, which started a large countrywide installation program in 2004.

During the past two years, Fingalson said, traffic engineers have come up with a new wrinkle for the rumble strips: instead of placing them outside the fog line, placing the fog line on top of the strips. The result, he and others said, is that the fog line is raised and its visibility -- especially in rainy weather -- is increased dramatically. "It's a new tool in our tool belt," Fingalson said.

But the change also leads to a large increase in the number of times motorists hit the strips. Fingalson said one out of 10 drivers was hitting the rumble strips last summer, which irritated neighbors. The problem was most acute along four areas where the road curved; there, drivers were more apt to skirt the edge of the driving lane or even cross over it.

That was the same problem in Carver County. Hemze said the road is so winding that the county felt it best to fill in the rumble strips.

"It's a balancing act between safety and noise pollution," Hemze said. "I can only imagine the things those people went through living out there."

Carver County Commissioner James Ische, whose office received numerous complaints, went so far as to go to the road and listen at various times of the day and night.

"What the residents were saying was true," said Ische, who went out one day at 4 a.m. The noise traveled "about two miles," he estimated. "You could hear them so far away that it was unbelievable."

Despite the problems, both counties said they will continue to use the rumble strips, especially along straight roadways. They also will look for ways to minimize the problems in other areas, especially if there are homes nearby.

"They do work," Fingalson said. "If people are hitting them, then they are working.

"Keeping people between the white lines -- that's what it's all about. We just have to tweak our criteria a little bit."